I have a part which has many layers of plating of different materials. In the model, I have modeled them as separte solid bodies and assigned material to each body. When I am in flow siulation, firstly I am not able to import the materials . Secondly, when I try to assign material, I am able to select the entire part only and not individual bodies (in this case different layers of plating).

Yes, I divided the body and then assembled them. This way I was able to assign materials. But the problem is having multiple very thin layers. These do play a major role in the thermal analysis. Yes, we can calculate approximate overall thermal conductivity in one direction by simplyfying the geometry (unlike in PCBs where you have uniform geometry with basic shapes). But it will lead to an error in this problem. ( will try anyways).

Also,wonder how much is the resolution (the minimum mesh size) solidworks can go upto, if there is a limitation?

Apparently, setting a goal paramter for the heater temperature and turing off/on the heater (heat source) when it reaches the specified value solved the issue .

I have one more issue, the solver is still solving even after reaching a goal (different goal- melting point of a body). Why is that? I have checked it for convergence criteria. Should I maually stop it every time it reaches thyat goal?